linux-kernel - Re: objtool warning for next-20221118

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Message-ID: <20221121145215.GF4001@paulmck-ThinkPad-P17-Gen-1>
Date:   Mon, 21 Nov 2022 06:52:15 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     jpoimboe@...nel.org, sfr@...b.auug.org.au,
        linux-kernel@...r.kernel.org
Subject: Re: objtool warning for next-20221118

On Mon, Nov 21, 2022 at 12:31:57PM +0100, Peter Zijlstra wrote:
> On Sun, Nov 20, 2022 at 08:07:36PM -0800, Paul E. McKenney wrote:
> > Hello!
> > 
> > I have started getting this from rcutorture scenario TREE09:
> > 
> > vmlinux.o: warning: objtool: do_idle+0x25f: unreachable instruction
> > 
> > Should I be worried?
> 
> Typically not a scary warning that.
> 
> > If so, please let me know what additional information you need.
> 
> .config and compiler version so that I might recreate and observe what
> it's complaining about would help :-)

Fair enough!  ;-)

.config is attached, and the compiler versions are:

gcc version 8.5.0 20210514 (Red Hat 8.5.0-15) (GCC)
gcc version 9.4.0 (Ubuntu 9.4.0-1ubuntu1~20.04.1) 

>From an RCU perspective, the key points about TREE09's .config is
CONFIG_PREEMPTION=y and CONFIG_SMP=n, but running on a single-CPU qemu
instance.

							Thanx, Paul

View attachment ".config" of type "text/plain" (134409 bytes)